Tree, Canopy & Microclimate

percent of land area · Observed by remote sensing, not by field survey. Trees shorter than eight feet were excluded from the assessment. The assessment was completed independently of the earlier Cambridge assessments and was not harmonised with them, so a comparison against 2009, 2014 or 2020 is general rather than exact.

acres · Same eight-foot height floor and same half-foot mapping resolution as the percentage. Rounded to whole acres by the publisher, which is why the gain and loss figures do not reconcile against the net change to better than an acre.

acres · The report publishes the 2024 acreage and the change but never the 2018 acreage. This is one subtraction over two published numbers, not a new measurement, and a reader can check it in the source drawer.

percent of land area · The report states both values itself and explains the difference as improved methodology and additional manual editing. It then contradicts its own prose: the time-period chart on the same page labels the lower value as the 2018 figure and the higher value as the 2020 figure. Same publisher, same page, two readings, neither withdrawn.

percentage points of land area · The published endpoints subtract to slightly less than the printed change; the difference is rounding in the source and is disclosed rather than silently corrected. The figure uses the revised 2018 baseline, so it inherits the unresolved dispute over which 2018 value is the right one.

percent change against the 2018 canopy area · This is the measure that proves why a formula field has to be visible. The published value is right and the source's own definition of it is not self-consistent, so the definition is printed beside the number and the discrepancy is recorded rather than resolved on the publisher's behalf.

acres · Gross, not net, and it must never be presented as an amount of new planting. The report attributes the largest share of gain to growth of existing canopy rather than to trees planted, and says so on the same page as the figure.

acres · This assessment does not attribute loss to a cause. It mixes construction clearing, storm damage and natural die-off, which the report states explicitly, so it cannot be read as a measure of removals and cannot be compared with the permit record.

percent of land area · Real published figures, and not comparable to the 2024 figure. The 2018-2024 study was completed independently of the earlier work and was not harmonised with it, though it kept the same spatial resolution, which the report says allows a general comparison and not an exact one.

acres, and percent of the land base · Biophysical possibility only. The report says this category should serve as a guide for further field analysis and not as a prescription of where to plant trees, and it names recreational fields as a direct conflict in use. It is capacity, never plan.

trees · The report states this is not a replacement for field-based inventories and is less accurate in forested stands where crowns may overlap. Trees under eight feet are excluded, and the estimate carries no species, no trunk diameter and no health, which the report also says explicitly.

trees · Maintained by the City is a responsibility boundary, not an ownership or a location boundary, and the page does not define it. It is not the street tree layer's row count and it is not the LiDAR estimate.

trees per five-foot height bin · Height is a proxy for age, not a measurement of it. Trees shorter than eight feet were excluded from the assessment entirely, so the short end of the distribution is a floor rather than an observation.

acres per height class · These are shifts in canopy area within each height class and not changes in the height of individual trees over time; the report states that explicitly. The comparison also uses a 2019 LiDAR capture for loss rather than the 2018 baseline the rest of the assessment is measured from, which is a discrepancy in the source and is recorded rather than smoothed over.

permits · Permits are issued removals rather than observed removals: an unpermitted removal appears only if enforcement records one. Coverage begins when the amended ordinance took effect, so there is no pre-ordinance baseline to compare against. THE YEAR IS THE YEAR THE PERMIT WAS ISSUED, NOT THE YEAR THE TREE CAME DOWN: the dataset publishes an application date, an issue date and two bond dates, and no removal date at all, so a permit issued in December may be executed the following year and there is no way to tell from the record. A count of trees removed in a year cannot be built from this feed, and none is published here.

permits per reason category · Two fields in this dataset answer the same question differently. Grouping on the reason category and grouping on the separate dead-or-dangerous flag do not produce the same count, and the dataset does not say why. This measure names the field it used.

permits carrying a diameter, per year · 2021 records 150 diameters, 150 species and 150 heights — the same figure three times, which is the signature of a records-system cutover partway through a year rather than of a decision. This measure states counts and does not attribute a cause. Urban Forestry has right of reply before any completeness finding is framed as a failure.

permits per neighbourhood · Two limits, both of them arithmetic rather than statistical. A small number of permits fall in no neighbourhood polygon at all and are published as their own figure rather than distributed. And a permit is a decision, not an observed removal: the record carries no date of removal and no confirmation that the tree came down, so this counts permissions granted in a place.

permits per 100 acres of 2018 canopy · This rate reorders the count, which is the reason it is published beside it: the neighbourhood with the most removals is also the neighbourhood with the most canopy, and reading the raw count as a ranking of loss gets the answer wrong. The denominator carries the water-inclusive polygon problem the neighbourhood canopy table already states, so the rate is comparable across these thirteen and against nothing else.

permits per neighbourhood per year · The withheld cells are not missing data. They were counted, they reconcile into the neighbourhood totals published beside them, and they are withheld because a single-figure count in a small neighbourhood plus one neighbour's memory of a tree coming down identifies a specific property. The suppression rule guarantees only that no withheld cell can be recovered by subtracting published figures from a published total; it does not claim to defeat an adversary who already knows most of the table.

cells, and permits inside them · This is the cost of the privacy rule, stated as a number rather than described. It is a large share of the cells and a small share of the permits, which is what a threshold does to a table whose mass sits in a few large neighbourhoods. Lowering the threshold would recover most of these cells and would also publish counts small enough to identify a property, which is the trade this figure exists to make visible.

percent of closed-year permits · The year-by-year measure beside this one shows a cutover; this one shows what the cutover costs when the whole period is read at once. The tree-count field moves the other way — empty before the cutover and partly filled after it — so the record did not simply degrade, it changed what it records. Urban Forestry has right of reply before any of this is framed as a failure.

unitless index · This is a modelled index of relative capacity and not a measured volume. The report publishes it as a map with a stated scale and publishes no per-place values in a table, so what is citable here is the scale and the method rather than any figure.

unitless index · The report's own legend describes the low end of the scale as areas that feel hotter, which is a felt comparison rather than a measured temperature difference. The index describes relative mitigation capacity, not degrees.

acres per patch class · These are the report's own prose figures, hedged in the source as nearly, over and approximately, and reproduced with the hedges intact. They describe structure and not habitat value: no species, occupancy or biodiversity figure for Cambridge is published, so habitat itself is a separate and empty measure.

inches of diameter at breast height, or dollars of equivalent value · This settles what is owed. It says nothing about when a replacement does the same work, and the ordinance does not claim otherwise — it is a payment rule that happens to be denominated in inches of trunk.

qualitative statement, quoted · This is the strongest published statement available and it is deliberately qualitative. Converting it into a number of years would be putting a figure into the publisher's mouth, which is what the neighbouring gap refuses to do.

percent of neighbourhood land area · The same neighbourhood has one of the highest relative increases over the period, which is what a large percentage change on a small base looks like. The two figures belong together and neither is quoted here without the other being one row away.

percent of neighbourhood land area, stated as a lower bound · The report gives no point estimate for this neighbourhood in prose. The exact figure sits inside a graphic whose underlying metrics table is not published, so the bound is what can honestly be stated.

percent change against the neighbourhood's own 2018 base · These are relative gains, so a neighbourhood with little canopy to begin with can post a large increase from a small absolute change. They are shown beside the coverage figures for exactly that reason, and the full per-neighbourhood table remains unpublished.

percent of the neighbourhood polygon, including water · The City states verbatim that no accuracy assessment was conducted on the source layer. It is a classified image product over LiDAR and imagery, not a tree census. The thirteen polygons also do not tile the city: 124.6 acres of 2018 canopy, 10.7% of the citywide extent, stands outside every one of them.

acres, and percent of the citywide 2018 canopy extent · This is why the neighbourhood set must not be read as a decomposition of the city. It is also why the thirteen sum to 1,039.8 acres, which is within half a percent of the 1,035 acres the later assessment states for 2018, while this record's own citywide figure sits 129 acres away from it.

inches of diameter, measured at four and a half feet above the ground · It applies to trees on a lot, as the ordinance defines a lot. The ordinance also excludes Affordable Housing Trust projects and qualifying low and moderate-income housing from the whole chapter, so protected-tree removals on those sites are outside the permit record by design.

project types · This is why the permit record is not a complete record of protected-tree removal in Cambridge, and the absence is deliberate policy rather than a data failure. The same section makes developers of fully affordable projects eligible to apply to the Tree Replacement Fund.

US dollars · The ordinance leaves the fee to the Commissioner, so it can change without an ordinance amendment and carries a short re-check cadence for that reason. The permit being free is not the same as removal being free; the mitigation rate is a separate measure.

US dollars per inch of diameter · The City calls it the current cost and derives it from its most recent tree planting and maintenance contract, inclusive of purchasing, planting, watering and maintaining trees for five years. It therefore moves with the contract and must be re-read on a short cycle rather than annually.

circumstances · This is the vocabulary and not the distribution. How often each circumstance is used is the removal-reason measure, which is not connected, and the two must never be presented as though the list implied a mix.

years · The category persists in the record for a decade, but nothing published states how many replacement trees were planted, how many survived, or how many were themselves later removed under this same provision.

days, and square feet · The twenty-one days is a minimum before filing rather than a decision period. The ordinance sets no published deadline for the City Arborist to decide an ordinary removal permit, and that separate gap is recorded as its own measure.

US dollars, and years of effect · Five thousand dollars is a floor, not the amount: the bond is set by the mitigation plan's total costs and only falls back to the floor when those are lower. Release requires the City Arborist to certify that the tree protection plan was met, and the owner must grant access for that check.

US dollars per day · The fine lives in the enforcement section, at its stop-work provision, its failure-to-comply provision and its alternative-penalty provision. The ordinance's duty-of-care section and the alternative-penalty provision both cross-reference the Tree Replacement Fund section for fines, which contains no penalty at all; that appears to be a drafting error in the source and is recorded rather than repeated.